Still got a skateboard buried somewhere in a corner of the garage? Celebrity personal trainer Mike Donavanik — http://www.mikedfitness.com — suggests you drag it out and repurpose it for this simple and effective fitness move, the skateboard pike.

What to do: Place the toes of both feet on the middle of a skateboard placed underneath you. Arms are on the ground in front in a push-up position. Using the core muscles, pull your feet toward your head as far as you can, keeping the head and spine aligned. Slowly return to the starting position — and repeat. To make this more challenging, try it with one leg on the board at a time; the other leg floats in the air.

How much: Depends on your fitness level. Beginner? Start with 10 reps. Intermediate? Try 20. If you're advanced, do the one-leg move — 10 reps each side. But just make sure you're listening to your body and don't push beyond your limits. Ease up if you feel you need to or if you feel any pain.